The rapid increase in small drone aircraft has introduced many beneficial applications of the technology. However, as with many new technologies, some malevolent activities emerge. Examples of these problematic activities are the flying of drones near airports and near prisons. The airport problem includes hobbyists that are unaware of the drone flying restrictions. The airport problem also includes terrorists attempting to fly drones into the engines of commercial and military airplanes in order to cause the airplane to crash. The prison problem includes individuals attempting to fly contraband (such as drugs or cell phones) over prison walls to a waiting prisoner. The present invention is a system and method to detect and locate a hostile signal transmitter when operating in a pre-defined geographical area for, as an example, the airport problem and the prison problem.